Arsenic may be on the verge of overcoming its
bad reputation. Two years ago, Chinese researchers reported that low
doses of arsenic trioxide induce remission in patients with acute
promyelocytic leukemia (APL), prompting physicians in the West to
undertake their own pilot study.

Researchers at Memorial Sloan-Kettering Cancer Center have now become
the first western investigators in the to show that arsenic
effectively induces remission in patients who have relapsed with APL.
The findings were reported in the New England Journal of Medicine.

We now know that arsenic can safely bring patients with APL
into remission, which may ultimately give them a second chance at
life, said Dr. Raymond P. Warrell, Jr, senior author of the
study and a leukemia specialist at Memorial Sloan-Kettering Cancer Center.

Arsenic Provides a Second Chance at Life

In the pilot study, 12 patients who had relapsed after conventional
therapy were treated with low doses of arsenic trioxide. Of the 12
patients, 11 achieved remission anywhere from 12 to 39 days after
arsenic treatment began, experiencing only mild side effects. The
single patient who did not go into remission died from a complication
related to the disease 5 days after arsenic treatment was initiated
and could not be evaluated in the study.

Once remission was achieved, each patient stopped treatment briefly,
then resumed repeat courses of arsenic trioxide therapy every 3 to 6
weeks, thereafter. After two cycles of therapy, investigators
conducted additional tests to determine whether any molecular
evidence of leukemia remained. Three patients tested positive for
disease and later relapsed with APL, while eight patients tested
negative and remained in remissions for as long as 10 months. To
date, several patients have received up to six courses of arsenic
treatment without experiencing cumulative side effects.

Expanded Role for Arsenic

Based on these highly sensitive molecular results, treatment
with arsenic trioxide appears to exceed the effectiveness of any
single drug used to treat APL, said Dr. Steven Soignet, lead
author of the study. Still, this is not a cure. More studies
will tell us how truly effective arsenic trioxide will be over the
long term.

This finding shows that arsenic trioxide does not
discriminate between APL that is resistant or not resistant to
retinoic acid, which may mean that we can use it at the outset of
treatment for patients with APL, said Dr. Soignet.

Clinical trials using arsenic trioxide to treat patients with APL are
ongoing at Memorial Sloan-Kettering and several other centers
throughout the country. Investigators will next look at the
effectiveness of arsenic trioxide in treating other types of cancers.

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